Lung cancer is of the highest incidence in the world. In China, the incidence of lung cancer ranks first among all cancers, and the incidence and mortality rates of the cancer are also the highest in China. In the lung cancer patients in China, 30% of patients have EGFR mutations, over 90% of which are L858R and exon 19 deletion-mutation, and these patients are more sensitive to EGFR inhibitors. The marketed first-generation of EGFR inhibitors, such as erlotinib, gefitinib have good effect for these patients, and the tumor in more than 60% of patients will shrink, significantly prolonging the progression-free survival of patients. However, most of patients acquire resistance in 6-12 months, the first generation of EGFR inhibitors will no longer take effect, and currently no drugs are available for these patients. EGFR T790M mutation is clinically detected in 50% of patients who are resistant to the first-generation of EGFR inhibitors. In T790M mutant cell line H1975, the activity of the first-generation of EGFR inhibitors, such as gefitinib and erlotinib, was greater than 3 uM, which means almost no activity.
The therapeutic effect of the second generation of irreversible pan-EGFR inhibitors (Afatinib (BIBW2992)) currently launched was significantly better than that of the first-generation of EGFR inhibitors for lung cancer patients with EGFR mutations. However, the second-generation of inhibitors also have strong inhibitory activity for wild-type EGFR, and the inhibitory activity for wild-type EGFR was significantly higher than that for resistant T790M mutation, and side effects, such as skin rashes, were severe in patients, and the effect of the second-generation of inhibitors on drug resistant patients was poor, only a small part of patients who are resistant to the first generation of EGFR inhibitors response to these drugs.
For improving the inhibitory activity for resistant T790M mutation while reducing the inhibitory activity for wild-type EGFR, it is of great significance to develop the third generation of selective inhibitors for EGFR mutants with higher activity, better selectivity, and lower toxicity. On the basis of the foregoing work, a variety of salts and polymorphs of inhibitors of EGFR mutants have been developed, which will facilitate further drug development.